Chemo‐Mechanical Energy Harvesters with Enhanced Intrinsic Electrochemical Capacitance in Carbon Nanotube Yarns

Abstract

Predicting and preventing disasters in difficult-to-access environments, such as oceans, requires self-powered monitoring devices. Since the need to periodically charge and replace batteries is an economic and environmental concern, energy harvesting from external stimuli to supply electricity to batteries is increasingly being considered. Especially, in aqueous environments including electrolytes, coiled carbon nanotube (CNT) yarn harvesters have been reported as an emerging approach for converting mechanical energy into electrical energy driven by large and reversible capacitance changes under stretching and releasing. To realize enhanced harvesting performance, experimental and computational approaches to optimize structural homogeneity and electrochemical accessible area in CNT yarns to maximize intrinsic electrochemical capacitance (IEC) and stretch-induced changes are presented here. Enhanced IEC further enables to decrease matching impedance for more energy efficient circuits with harvesters. In an ocean-like environment with a frequency from 0.1 to 1 Hz, the proposed harvester demonstrates the highest volumetric power (1.6-10.45 mW cm −3 ) of all mechanical harvesters reported in the literature to the knowledge of the authors. Additionally, a high electrical peak power of 540 W kg −1 and energy conversion efficiency of 2.15% are obtained from torsional and tensile mechanical energy.

Omnidirectional Energy Harvesting Fleeces

“…Because of the inherent softness of the fleece structure, the mechanical input stress required to drive the SWCNT/wool energy harvester is approximately 15,000 times lower than that of other chemo-mechanical energy harvesters. As a result, the proposed SWCNT/wool energy harvester achieved the highest SCC to input stress ratio (> 10 2 ) among chemo-mechanical energy harvesters reported so far 4,7,8,31 (Figure 2f). Such extremely sensitive responsiveness to mechanical loads is an important factor in ensuring the operation of the harvester even with small external forces, maximizing its operability in real environments.…”

“…Underwater mechanical energy harvesters are promising devices that electrochemically generate electrical energy in electrolyte environments by external mechanical energy. − The device uses the ions dissolved in deionized water as the main power source, and depending on the type, it has the potential to utilize even the ions present in waterfall or natural seawater . The primary goal is to convert spontaneously generated mechanical energy, such as wind and ocean currents, into electrical energy.…”

“…The two main types of underwater mechanical energy harvesters reported to date are liquid–solid triboelectric nanogenerators − and chemo-mechanical energy harvesters. − Both types produce electrical energy through a change in the area of an electrically or electrochemically charged surface area under mechanical force. The development direction of such energy harvesters has been focused on maximizing output power while minimizing performance drop by repeated cycles.…”

“…1−7 The device uses the ions dissolved in deionized water as the main power source, and depending on the type, it has the potential to utilize even the ions present in waterfall 2 or natural seawater. 7 The primary goal is to convert spontaneously generated mechanical energy, such as wind and ocean currents, into electrical energy. Therefore, underwater energy harvesters are likely to expand to a variety of applications, such as current monitoring devices or wave sensors for the management of marine ecosystems.…”

Soft Fiber/Textile Actuators: From Design Strategies to Diverse Applications

“…Later, a coiled CNT yarn actuator with peak electrical power up to 540 W kg −1 at 12 Hz cycles, increasing the energy conversion efficiency to 2.15% were reported. 202 In addition, a plied CNT yarn can further increase the energy conversion efficiency. For example, the energy conversion efficiency of tensile actuation increased from 7.6% to 17.4%, and the energy conversion efficiency of torsional actuation reached 22.4%.…”